Final answer:
Two objects may hit the ground with equal velocities if air resistance affects both equally and they were launched with the same initial velocity. This is because gravity causes all objects to accelerate at the same rate if air resistance is negligible. so, option D is the correct answer.
Step-by-step explanation:
In a scenario where two objects are projected downward, they might hit with equal velocities if air resistance affects both equally (C) and they were launched with the same initial velocity (D). The key principle here is that all objects in a given location fall toward the center of Earth with the same constant acceleration, independent of their mass, as long as air resistance and friction are negligible. Galileo's experiments, along with Einstein's considerations, affirm that without air resistance, two objects would accelerate at the same rate due to gravity, regardless of their mass.
An example illustrating this principle involves two people jumping into a chasm from opposite sides. Assuming no air friction, they would fall and accelerate downward at the same rate. Thus, if two objects are thrown downward with the same initial velocity and are influenced equally by air resistance, they would hit the ground with equal velocities.